#include <stdio.h>

char a[] = "hello world";

int index_of(char letter) {
	int i=0;
	while(a[i] != '\0') {
		if(a[i] == letter) {
			return i;
		}
		i ++;
	}
	return -1;
}

int main(int argc, char *argv[]) {
	printf("%d %d\n", index_of('o'), index_of('z'));
	return 0;
}

